The present invention relates generally to the field of magnetic data storage and retrieval systems. In particular, the present invention relates to a magnetic read head having a shield/electrode structure in which the magnetic and electrical functions thereof have been separated from one another.
In a magnetic data storage and retrieval system, a magnetic recording head typically includes a reader portion, or read head, having a magnetoresistive (MR) sensor for retrieving magnetically encoded information stored on a magnetic medium, such as a magnetic disc. To retrieve information from a track of the magnetic disc, the read head is positioned over that track as the disc is rotated at a high speed. This rotation causes the read head to be supported over an air bearing surface (ABS) of the magnetic disc by a thin cushion of air. To ensure that the MR sensor reads only the information that is stored directly beneath it on a specific track of the magnetic disc, first and second magnetic shields are placed on either side of the MR sensor.
During a read operation, magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer or layers of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor. The change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor. Depending on the geometry of the device, the sense current may be passed in the plane (CIP) of the layers of the device or perpendicular to the plane (CPP) of the layers of the device.
To provide current to the MR sensor of a CPP read head, the first and second magnetic shields conventionally perform double duty as both magnetic shields and electrodes. Optimization of the various electrical and magnetic functions required of the magnetic shields for a CPP MR sensor requires conflicting demands on their physical structure. There is thus a need for a magnetic shield/electrode structure for a MR sensor of a CPP read head in which both the magnetic and electrical functions of the CPP read head can be optimized.